Do chest x-rays and mammograms increase the risk of breast cancer in young women?

Some women already at high risk of breast cancer should be cautious about having mammography or chest x-rays before the age of 30 because the imaging may increase the risk of developing the disease, researchers here said.

Five or more x-rays, or any exposure to ionizing radiation before age 20, increased the likelihood of breast cancer two-and-a-half times in this high-risk group, Marijke C. Jansen-van der Weide, PhD, of the University Medical Center Groningen in the Netherlands, and colleagues reported at the Radiological Society of North America meeting.

“For women at high risk for breast cancer — those with high-risk mutations of a family history of breast cancer — screening is very important, but a careful approach should be taken when considering mammography for screening young women, particularly those under the age of 30,” Jansen-van der Weide said.

But she cautioned that the findings do not apply to the general population. Women who are at an increased risk of breast cancer have a mutation in a damage-repair gene, which makes them more susceptible to the effects of DNA-damaging ionizing radiation. Most women do not have this mutation.

To assess how low-dose radiation exposure affects breast cancer risk, the researchers conducted a meta-analysis of six studies — half of which showed an increased risk of cancer, and half that didn’t — totaling 9,420 women.

They found that high-risk women had a 2.5-fold increased risk of developing breast cancer compared with women in the general population (95% CI 1.6 to 3.9).

Those who had x-rays before they were 20 also had a 2.5-fold increased risk of developing breast cancer (95% CI 1.9 to 3.2).

And while x-ray screening after 20 carried a 1.5-fold increased risk of breast cancer, it was not significant, Jansen-van der Weide said.

“For high-risk women, it is important to screen for breast cancer,” she said. “But they should weigh the risks and benefits with their doctors to come up with a screening strategy.”

Jansen-van der Weide recommended starting screening at age 30, and going back every other year. Also, the possibility of using alternative techniques, such as magnetic resonance imaging (MRI), may be appropriate for high-risk women in this age group.

She called for future prospective studies to get a more accurate estimation of cancer risk from radiation exposure.

Mary C. Mahoney, MD, of the University of Cincinnati Medical Center and vice president of public information for RSNA, said the study deals with a very small population of breast cancer patients, “only 5% of all breast cancers.”

She emphasized that the findings do not apply to the general population.

Stephen Feig, MD, of the University of California Irvine, a spokesperson for RSNA, said the study has many limitations, including its retrospective nature which did not permit a good analysis of radiation doses.